This is the symptom of jaw crusher.

The possible reason is as follow:

1.  The discharge gate of jaw crusher was clogged, causing the chamber filled with plugging materials

2.  The V-belt which drives the scored pulley is loose, causing the belt slip off

3.  The voltage is lower, so the main frame is hard to crush the large material.

4.  Bearing is broken.

The way to resolve:

1.  Get rid of the obstruction, to ensure the charge gate is clear.

2.  To tighten or replace the V-belt.

3.  Adjust the voltage to suit to main frame working requirement.

4.  Replace the bearing.